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ELECTRIC IMPEDANCE OF NITELLA DURING ACTIVITY.
1Department of Physiology, College of Physicians and Surgeons, Columbia University, New York.
The Journal of General Physiology
|October 30, 2009
Summary
Electrical activity in Nitella cells causes significant changes in cell membrane impedance. Membrane resistance drops dramatically during excitation, indicating a rapid electrical response.
Area of Science:
- Plant electrophysiology
- Cell membrane biophysics
Background:
- Cellular activity involves complex electrical changes.
- Understanding membrane properties is crucial for cell function.
Purpose of the Study:
- To measure alternating current (AC) impedance changes during Nitella cell activity.
- To correlate impedance variations with action potential dynamics.
Main Methods:
- AC impedance measurements at eight frequencies (0.05–20 kHz).
- Wheatstone bridge and cathode ray oscillograph used for measurements.
- Electrical stimulation and motion picture recording of oscillograph output.
Main Results:
- Membrane capacity decreased by ~15% without phase angle change.
- Membrane resistance decreased from 10^5 to ~500 ohm cm^2 during excitation.
- Membrane changes occurred late in the action potential's rising phase.
Conclusions:
- Cell membrane resistance significantly decreases during excitation.
- Action potential involves passive potential fall preceding membrane changes.
- Electromotive force remains stable until late in the action potential.
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